What are the key differences between revamp and grassroots design?

Revamp design modifies existing plant; grassroots builds new. Revamp challenges: Equipment constraints - must work with existing equipment, sizes, materials. Documentation - original drawings may be incomplete or inaccurate; field verification essential. Tie-ins - minimize shutdown time, plan hot/cold cuts carefully. Relief systems - verify existing capacity for new conditions. Utilities - check available capacity for increased loads. Constructability - work in operating plant, limited space, confined areas. Operating constraints - often must maintain production during modification. HAZOP scope - focus on changes but consider interaction with existing. Advantages of revamp: lower capital (utilize existing equipment), faster implementation, lower risk (known site conditions). Grassroots advantages: optimal design without constraints, clean documentation, easier construction. Revamps often compromise technical optimum for practical implementation.